The Children's Heart Program of South Carolina, with MUSC as the tertiary referral center, is a statewide consortium of pediatric cardiologists, who care for >90% of the 4.0 million residents in the state. This consortium has all the critical elements for a center in the PHN: adequate patient volume, clinical research infrastructure, a track record of subject enrollment, and a dedication to hypothesis driven clinical research. Indeed, these elements have allowed MUSC to be a highly successful participant in the PHN. Further, MUSC faculty have participated as Pi's in a large number and wide variety of multicenter trials or registries, and the Pi's of this proposal have often been the lead investigator. MUSC faculty also currently run numerous local clinical research protocols. Participation in all of these protocols is supported by a dedicated pediatric cardiac research support group with RN coordinators and an administrative FTE. The combined resources of patient volume and strong research infrastructure have enabled MUSC to be among the top subject enrollers as well. Protocol: Randomized Trial of Preoperative Corticosteroid Therapy in Neonates Undergoing Cardiopulmonary Bypass (CPB). CPB is critical to corrective intracardiac surgery, but the pathophysiologic processes engendered by CPB, particularly in neonates, play an important role in post- CPB recovery. The use, doses and schedule of glucortocoid administration to ameliorate these CPB induced processes appears to be highly variable among pediatric cardiac surgical centers, without clear data to provide direction. The Primary Aim of this study is to compare the effects of preoperative intravenous methypredisolone (IVMP) to placebo on the Primary Endpoint of low cardiac output state (LCOS) or death at 36 hours following neonatal CPB. We hypothesize that neonates receiving preoperative IVMP will have a decreased incidence of the Primary Endpoint. Secondary Endpoints include: inotropic score at 36 hours, fluid balance, ICU stay parameters, echocardiographic measures, levels of inflammatory molecules, and safety parameters. One unique aspect of the protocol is the use of a novel multiplexer technology which allows analysis of a broad array of cytokines, matrix metalloproteinases and myeloperoxidase from a sample of one milliliter or less of whole blood. The results of this study should clearly define the clinical utility of preoperative steroids and help determine the mechanisms for any observed effect. (End of Abstract).